My guess is that you'll need to manually enter the data for one of the two accounts (I suggest the one with fewer transactions...).  Give the brokerage name a slightly different one than the one you'll be uploading

Did you go to TD Website and read the instructions there ??

You should have no trouble, no matter how many accounts you have with TD.

TurboTax Online has some really serious user interface problems that cause so much confusion.

You can't choose the TD name box showing once you used it for the first account.

You have to enter the TD name again